diff --git a/src/libstrongswan/plugins/openssl/openssl_pkcs7.c b/src/libstrongswan/plugins/openssl/openssl_pkcs7.c
index 251174283..663397e59 100644
--- a/src/libstrongswan/plugins/openssl/openssl_pkcs7.c
+++ b/src/libstrongswan/plugins/openssl/openssl_pkcs7.c
@@ -13,6 +13,8 @@
  * for more details.
  */
 
+#include <openssl/opensslconf.h>
+
 #ifndef OPENSSL_NO_CMS
 
 #include "openssl_pkcs7.h"